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PubMed2005

The consent and counselling of patients for cataract surgery: a prospective audit.

PURPOSE: The aims of ideal preoperative informed consent include educating the patient adequately to enable an autonomous decision to be made without causing undue anxiety. We study how the paternalistic and nonpaternalistic approaches meet this ideal. The influence of the new patient consent forms is also assessed. METHODS: Two cycles of a prospective clinical audit are presented. An assessment of relevant patient knowledge was performed by patient interview. Visual analogue scales were used to quantify patient anxiety. RESULTS: The first cycle, examining a paternalistic approach, demonstrated: 37% of patients understood what a cataract was and 48% understood what surgery involved. 48% misunderstood that cataract surgery was completely risk free. In total, 80% of patients undergoing second eye surgery believed that it was completely risk-free. Average anxiety visual analogue scores (VAS) for cataract surgery were low (2.89). The second cycle, examining the nonpaternalistic approach combined with the implementation of new consent forms showed that, despite more explicit repeated preoperative consent: 39% of patients understood correctly what a cataract was, 28% understood what surgery involved and 43% misunderstood that surgery was completely risk-free. All patients undergoing second eye surgery thought that it was risk-free. The average anxiety VAS for cataract surgery were moderate (5.00). CONCLUSIONS: Both paternalistic and non-paternalistic approaches to informed consent are inadequate in meeting the demands of the ideal informed consent. The new patient consent forms appear to have little effect in influencing patient knowledge about their surgery. Patients undergoing second eye surgery often have an overoptimistic view of cataract surgery.

Aged↗

PubMed2006

Hormone replacement therapy and cataract: a population-based case-control study.

PURPOSE: Laboratory studies have suggested that hormone replacement therapy (HRT) may protect against the development of cataract, but epidemiological studies in humans have thus far been inconclusive. The aim of this study was to assess the association between hormone replacement therapy and cataract. METHODS: Population-based case-control study using data from the General Practice Research Database in the UK. Participants were 10 000 women aged 45 years and over with diagnosed cataract and 10 000 controls matched on age, general practice, and calendar period. RESULTS: The crude odds ratio for the association between cataract and ever-use of oestrogen-only hormone replacement therapy was 1.13 (95% CI 0.99-1.29). This reduced to 0.81 (95% CI 0.71-0.94) after adjustment for consultation rate. Similarly, the crude odds ratio for the association between cataract and ever-use of a formulation containing oestrogen and progestogen was 1.18 (95% CI 1.01-1.39), reducing to 0.86 (95% CI 0.72-1.02) after adjustment for consultation rate. CONCLUSIONS: Oestrogen-only and oestrogen-progestogen hormone replacement therapies are associated with a small reduced risk of cataract. This data adds to the growing body of evidence on the effects of HRT on health. All potential benefits and risks of this therapy should be taken into account when considering its use.

Aged↗

PubMed2006

Comparison of epilenticular IOL implantation vs technique of anterior and primary posterior capsulorhexis with anterior vitrectomy in paediatric cataract surgery.

PURPOSE: To compare the functional outcome of epilenticular intraocular lens (IOL) implantation vs the technique of anterior continuous curvilinear capsulorhexis (ACCC), posterior continuous curvilinear capsulorhexis (PCCC) with vitrectomy and in-the-bag IOL implantation in paediatric cataract surgery. METHODS: Forty eyes of 33 children with developmental or traumatic cataract, whose mean age was 2-12 years, were randomly divided into two groups A and B. Group A patients underwent epilenticular IOL implantation while in group B patients, ACCC, PCCC with anterior vitrectomy with in-the-bag IOL implantation was performed. Equal number of eyes (10 each) with developmental cataracts (subgroups A1 and B1) and traumatic cataracts (subgroups A2 and B2) were allotted to both the groups. Postoperative visual acuity, opacification of the visual axis, and possible complications were observed and analysed. RESULTS: Four eyes in subgroup B2 had fibrous or ruptured capsules, and were managed by epilenticular IOL implantation technique. One eye in subgroup B2 developed central posterior capsular opacification and hence required a secondary capsulotomy. All cases in group A maintained a clear visual axis at the last follow-up. Minimal postoperative inflammation was noticed in all groups, which subsided with anti-inflammatory medication. At the last follow-up, all eyes in group A gained visual acuity >/=6/18. Whereas in group B, visual acuity >/=6/18 was obtained in 85.7% cases with the epilenticular IOL implantation technique and in 83.3% cases with ACCC and PCCC with anterior vitrectomy technique. CONCLUSION: Epilenticular IOL implantation offers a safe and effective alternative for management of paediatric cataract. In selected cases of traumatic cataract, it is the preferred treatment modality.

Capsulorhexis↗

PubMed1995

Relationship between serum tryptophan and tryptophan metabolite levels after tryptophan ingestion in normal subjects and age-related cataract patients.

1. Cataract is the single major cause of blindness worldwide; however, the reasons for the development of this condition remain unknown. It has been suggested that the essential amino acid tryptophan may be implicated in the aetiology but definitive evidence has been lacking. 2. The serum levels of tryptophan and seven of its metabolites have been measured in both cataract patients and control subjects, after administration of tryptophan, in order to determine the typical response profile and to discover whether differences could be found in tryptophan metabolism in the two groups. 3. Tryptophan, kynurenine, kynurenic acid, xanthurenic acid, 3-hydroxyanthranilic acid, 5-hydroxyanthranilic acid, 5-hydroxytryptophan and anthranilic acid were measured by HPLC with dual electrochemical and programmable wavelength fluorescence detection. Fasting cataract patients (n = 42) and control subjects (n = 37) were given an oral dose of L-tryptophan and sera were sampled at 0, 1, 2, 4 and 6 h. 4. Statistically significant differences in the distribution of data between the two groups were observed. The responses of kynurenine and 5-hydroxyanthranilic acid were higher in cataract patients, but those of kynurenic acid and total tryptophan were lower than in control subjects. No statistically significant differences in free tryptophan, anthranilic acid, 3-hydroxyanthranilic acid, xanthurenic acid or 5-hydroxytryptophan levels were noted. 5. We conclude that there is a major subgroup of age-related cataract patients with a dysfunction in the metabolism of tryptophan. This may be related to the onset of cataract. The mechanism remains to be established but may operate via the action of tryptophan metabolites, such as 5-hydroxyanthranilic acid, which become reactive towards protein upon oxidation.

Age Factors↗

PubMed2001

Clinical, biochemical and molecular findings in a series of families with hereditary hyperferritinaemia-cataract syndrome.

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant disease caused by mutations in the iron responsive element (IRE) of the l-ferritin gene. Despite the elucidation of the genetic basis, the overall clinical spectrum of HHCS has been less well studied as, to date, only individual case reports have been described. Therefore, we studied a total of 62 patients in 14 unrelated families, with nine different mutations. No relevant symptoms other than visual impairment were found to be associated with the syndrome. A marked phenotypic variability was observed, particularly with regard to ocular involvement (i.e. age range at which cataract was diagnosed in 16 subjects with the C39T: 6-40 years). Similarly, serum ferritin levels varied substantially also within subjects sharing the same mutation (i.e. range for the A40G: 700-2412 microg/l). We followed an HHCS newborn in whom well-defined lens opacities were not detectable either at birth or at 1 year. The lens ferritin content was analysed in two subjects who underwent cataract surgery at different ages, with different cataract morphology. Values were similar and about 1500-fold higher than in controls. These observations suggest that: (i) in HHCS the cataract is not necessarily congenital; (ii) in addition to the IRE genotype, other genetic or environmental factors may modulate the phenotype, especially the severity of the cataract.

Adolescent↗

PubMed2001

Lower nasal distribution of cortical cataract: the Blue Mountains Eye Study.

Previous reports have indicated that cortical cataract commences in the lower nasal lens, possibly due to sunlight exposure because of the shallow brow temporally. The present study aimed to assess the lens sector distribution of cortcal cataract in a population. The Blue Mountains Eye Study assessed 3654 residents aged 49-97 years; 3270 phakic subjects had retroillumination lens photographs graded using the Wisconsin method, which divides the lens into eight radial sectors with a grid overlay. Graders estimated percentage of cortical opacity in each sector. The lower nasal area consistently had the greatest opacity, a pattern present at each age and similar in both sexes, despite the 20% greater cortical cataract in women. The mean area of lens cortex involved by opacities in the lower nasal hemisphere was four fold greater than in the upper temporal hemisphere at each age. The lower nasal distributon was highly symmetrical when both eyes were affected. When > 20% of the lower nasal lens quadrant had cortical opacity, 88% of bilaterally affected subjects had cortical cataract n the same quadrant of the fellow eye. The lower nasal distribution may indicate a role for sunlight in the aetiology of cortcal cataract, which could be considered when examining other cortical cataract risk factors, such as diabetes, vascular disease and hormonal factors in women.

Age Distribution↗

PubMed2000

[Cataract surgery in 79 patients with relative anterior microphthalmus (RAM): a review of anatomy, associated pathology and complications].

BACKGROUND: Naumann has coined the term relative anterior microphthalmus (RAM) for eyes with a dysproportional small anterior segment but no further malformation. Those eyes are characterized by corneal diameters of < 11 mm and total axial length of > 20 mm. PATIENTS AND METHODS: To evaluate and define morphometrical data and risk factors for cataract surgery in patients with relative anterior microphthalmus (RAM) 112 cataract operations of 79 patients with RAM were analysed. Associated ocular pathology (such as glaucoma, previous surgical interventions, etc.) and complications of cataract surgery were recorded. RESULTS: Average corneal diameter was 10.7 +/- 0.34 mm, AC-depth was 2.20 +/- 0.49 and average lens thickness 5.05 +/- 0.45 mm. Fifty five percent of the patient revealed myopic refraction. There was a high incidence of glaucoma (77%), cornea guttata (46.6%) and Pseudoexfoliation syndrome (16%) in the RAM-group. Sixty percent of patients previously underwent glaucoma surgery. After cataract surgery 51.2% of patients achieved a visual acuity of > 0.5; 69.8% > 0.4. The IOP was preoperatively 16.5 +/- 5.8 mm Hg (with 1.3 +/- 1.4 antiglaucomatous drugs). Postoperatively IOP dropped significantly to 13.6 +/- 3.2 mm Hg (with significant reduction of treatment (0.6 +/- 1.0) (p < 0.01). The anterior chamber depth deepened from 2.42 +/- 0.47 mm to 3.33 +/- 0.72 mm. CONCLUSIONS: The special anatomical situation in RAM is responsible for the high incidence of glaucoma and postoperative complications after cataract surgery. Cataract surgery helps not only to restore vision but also facilitates handling and regulation of intraocular pressure.

Aged↗

PubMed2003

[Simultaneous bilateral cataract extraction--a retrospective study].

BACKGROUND: In patients with bilateral cataracts and contraindications for local anaesthesia a simultaneous bilateral cataract extraction under general anaesthesia is worth considering. PATIENTS AND METHODS: The retrospective study includes all 19 patients (aged 58 to 94 years, mean age 81.5 years) who underwent simultaneous bilateral cataract extraction at our hospital in a period of two years. While the majority of patients had bilateral phacoemulsification, five eyes of three patients underwent planned extracapsular cataract extraction. The preoperative ophthalmic and anaesthetic data and the perioperative and postoperative follow-up data are evaluated. Additionally patient satisfaction and financial aspects are investigated (coverage of the second eye surgery by health-insurance). RESULTS: In none of the 19 patients did severe complications occur. The majority of patients showed a fast visual rehabilitation with a striking improvement in their quality of life. The majority of eyes (20/38; 52.6 %) achieved a visual acuity of 20/30 or better. The analysis of financial aspects disclosed disadvantages for the hospital. CONCLUSIONS: Simultaneous bilateral cataract extraction can be considered as a safe and effective method for a selective group of patients with bilateral cataracts.

Aged↗

PubMed2004

Comparing phacoemulsification and extracapsular cataract extraction in eyes with pseudoexfoliation syndrome, small pupil, and phacodonesis.

BACKGROUND: This study aims to compare the frequency of intraoperative and postoperative complications between the modern phacoemulsification technique and the extracapsular cataract extraction technique in patients with pseudoexfoliation syndrome. PATIENTS AND METHODS: A prospective randomized study comprised 94 eyes with cataract, pseudoexfoliation syndrome, small pupil and slight to moderate phacodonesis. These eyes were randomly assigned into two groups. In the first group all patients (47 eyes) were operated on using a standard phacoemulsification technique (iris hooks, anterior capsule staining and capsular tension ring after capsulorhexis), while in the second group all patients (47 eyes) underwent a classic extracapsular cataract extraction. The main outcome measures were the frequency of intraoperative zonular tears, capsular rupture, vitreous loss and corneal edema, as well as the best-corrected visual acuity. RESULTS: Intraoperative zonular separation was recorded in one eye (2.1 %) and in 15 eyes (31.9 %) for the first and second groups, respectively (P < 0.001). Posterior capsule rupture with or without zonular separation occurred in two eyes (4.2 %) of the first group and in eight eyes (17.0 %) of the second group (P < 0.05). Vitreous loss also had a higher rate in the second group (17.0 % versus 4.2 %, P < 0.05). The postoperative difference in best-corrected visual acuity was also significant between the two groups, being higher in patients operated on using phacoemulsification technique (P < 0.001). CONCLUSIONS: In the difficult cases of cataract associated with pseudoexfoliation syndrome, small pupil and phacodonesis, the modern small-incision cataract surgery provides better results with a low rate of intraoperative and postoperative complications when compared with the extracapsular cataract extraction technique.

Aged↗

PubMed1999

[Familial cataract in plasma galactitol increase without known enzyme defect].

BACKGROUND: Several enzyme defects of the galactose pathway may lead to cataract formation. We report on a family with familiar cataract. PATIENTS: A 2-year-old Turkish girl (daughter of first cousins) presented with dense cortical and subcapsular opacifications and mature cataract respectively. Bilateral phacectomy, planned posterior capsulotomy, transpapillary vitrectomy and implantation of a posterior chamber lens were performed. The child was otherwise healthy and the pregnancy had been unremarkable. The 25-year-old mother showed circumscribed drop-like opacities of the lens cortex bilaterally, the 5-year-old sister a diffuse opacification of the lens cortex in both eyes, the 27-year-old father and the 13-year-old uncle clear lenses. RESULTS: The girl's level of galactitol was elevated to 2.8 nmol/ml in the plasma (normal values 0.25-1.13 nmol/ml) and to 3.1 nmol/mg protein in the lens (normal values 0.5-1.7 nmol/mg protein). The levels of galactose-1-phosphate in RBC and sorbitol in plasma were in the normal range. The enzyme activities of galactokinase, galactose-1-phosphate uridyl transferase, UDP-galactose epimerase and sorbitol dehydrogenase in RBC, as well as the sorbitol dehydrogenase activity in the lens were in the normal range. The sister and the uncle both had slightly elevated plasma galactitol levels. CONCLUSIONS: Cataract-formation in this family is most likely due to a defect in the galactitol pathway, e.g. cataract in galactosemia without known enzyme defect (Shin-Jakobs disease). In patients with unexplained congenital or infantile cataracts, disorders of the polyol pathway should be thoroughly checked for to ensure a therapeutic diet if necessary.

Adult↗

PubMed1994

[Pseudoexfoliation syndrome--a risk factor in modern cataract surgery?].

BACKGROUND: The pseudoexfoliation (PEX) syndrome has been described in the ophthalmic literature as a major risk factor of cataract surgery. Most of the authors have reported extracapsular cataract extraction (ECCE) complication rates of more than 10% for zonular dialysis, capsular rupture, and vitreous loss. However, Osher et al. (1993) found that these complications from in situ phacoemulsification (PE) cataract surgery were less than 1%. We compared ECCE with PE by using the same surgeons for both procedures and evaluated retrospectively the complications for each in our patients. PATIENTS AND METHODS: Of 10,450 patients who underwent cataract surgery from 1986 to 1993, 102 PEX cases (0.98%) occurred. ECCE was performed on 34 of these patients, PE on 68 of the 102 patients. The average age of the PEX patients was 78 years. Miosis of 4 mm or less occurred in 19 eyes. To dilate the pupils, sphincterectomies were performed and iris retraction hooks were applied to the iris in the last two years. Eight surgeons (four with long-term experience and the remainder in training) performed the operations. RESULTS: The complication rates were 16.6% altogether for zonular dialysis, capsular rupture and vitreous loss, 26.47% for ECCE, and 11.76% for PE (p = 0.0664), in contrast to 1.3% for uncomplicated age-related cataract operations. However, these complications occurred in 14.28% of the ECCE patients and 9.09% of the PE patients with more or less normal dilation of the pupil. Still PE with miosis had fewer complications (23.07%) and was, thus, significantly safer (p = 0.0022) than ECCE (83.33%). Slight phakodonesis, observed during capsulorhexis, and an additional diagnosis of chronic open-angle glaucoma did not provide significant differences between the two surgical methods resulting in PEX. CONCLUSION: Miosis is beside phacodonesis the primary risk factor of PEX associated with cataract surgery. Compared with ECCE, PE had significantly fewer complications from PEX with miosis, not from PEX with phacodonesis. Applying the small iris retraction hooks appeared to decrease the complication risks stemming from miosis.

Adult↗

PubMed1991

[Is there an ideal surgical time for retinitis pigmentosa patients with cataract?].

According to the literature, a fully developed cataract should be removed generally when the macula is intact. However, patients with a slowly progressing retinal disease find themselves in a particularly difficult situation. In this clinical, retrospective study, 24 retinitis-pigmentosa (RP) patients after cataract surgery were asked whether they recommend cataract surgery early or late in the course of the development of the retinal disease. A correlation was found between the answers to this question and the time elapsed between each patient's own operation and his interview. Three preference groups resulted through statistical evaluation: 1) those who recommend an early operation (n = 8), 2) those who recommend a late operation (n = 8), and 3) those who were undecided (n = 8). All patients had been operated at the same time following the RP onset and cataract diagnosis. Those patients who preferred a late operation had been questioned in this regard considerably later after their own operation than those who preferred an early operation. In other words, the preference for an early or late operation depended on how much prior to the questioning the patient's own operation had been conducted. The RP patient, quite disease conscious, has an exact conception of the ideal time of cataract operation in RP patients in general, but this does not always coincide with the opinion of his physician. It is considerably more necessary to consider the individual situation of the RP-patient than that of normal cataract patients.

Cataract Extraction↗

PubMed1988

[A table of senile forms of cataract. Clinical picture, prognosis, biochemistry and etiology].

The three important types of age-related senile cataract, namely deep supranuclear cortical cataract, superficial subcapsular cortical cataract (sometimes associated with secondary nuclear cataract), and primary nuclear cataract, are arranged in a table which may be used for quick reference with regard to clinical features - slit lamp findings, age at onset of opacification, rate of progression, and related biochemistry (e.g., ATP content, glutathione content, and the cation pump (K+ greater than Na+] - as well as etiological features. The significance of the table is illustrated on the basis of an important example from the literature ("Sunlight and Human Cataracts").

Adenosine Triphosphate↗

PubMed1985

[What possibilities exist to modify cataract development on the basis of current biochemical knowledge? Where can drugs act?].

During the last 10-15 years, investigations into the biology and biochemistry of the lens have demonstrated that the age changes observed cannot be the only cause of the formation of senile cataract. The various types of opacities and the wide age range in which they begin indicate a multifactorial origin involving endogenous and exogenous risk factors. Initial epidemiological studies have identified certain risk factors. Experimental cataract research is able to elucidate possible damaging mechanisms by using cataract models, for instance, the cataracts caused by excess carbohydrate (galactose, glucose), naphthalene application, ionizing rays, or by additional cocataractogenics, thus indicating steps for countermeasures. Taking (true) diabetic cataract of rats after Streptozotocin injection as an example, the efficacy of aldose reductase inhibitors is shown. Even if additional cataractogenic factors such as naphthalene and X-rays are applied, diabetic lens opacities can be prevented completely. Damage by naphthalene is due to an increased oxidative change in the lens protein. Several substances promoting the antioxidative capacity of the lens, thereby inhibiting cataract formation, are already available. Preclinical or clinical studies have demonstrated the efficacy of only a few of the commercially available anticataract drugs. The results of animal experiments presented here may well represent a basis for the development of really effective anticataract drugs.

Aging↗

PubMed2002

Case series of 12 children with progressive axial myopia following unilateral cataract extraction.

PURPOSE: We report the occurrence of unilateral progressive axial myopia ipsilaterally in a retrospective analysis of 12 children following uniocular cataract surgery. METHODS: A retrospective analysis of the case records of children who had developed progressive ipsilateral axial myopia following unilateral cataract surgery was done. Follow-up ranged from 4 years to 14 years. RESULTS: Twelve children, 7 male and 5 female, were eligible for the study. Mean age at the time of cataract surgery was 6.7 +/- 2.5 years (range, 4-11 years) and follow-up period was 7.8 +/- 3.1 years (range, 4-14 years). Ten children (83.3%) had traumatic cataracts of which 8 had undergone repair of penetrating eye injuries and 2 had suffered blunt trauma. Two patients (16.7%)had been operated for unilateral developmental cataracts. Three children had aphakia and nine had pseudophakia. Degree of myopic shift ranged from -4.75 D to -15 D (mean, -7.35 +/- 3.51 D). Axial length difference between the 2 eyes ranged from 1 mm to 3.5 mm (mean, 2.2 +/- 0.9 mm). Mean increase of axial length from preoperative recording to final follow-up was 2.53 +/- 0.90 mm (range, 1.6-4 mm). Three children had to undergo IOL explantation and 1 had posterior chamber intraocular lens exchange due to high unilateral myopia. The rest were visually rehabilitated with either spectacles or contact lenses. CONCLUSION: Following cataract surgery pediatric eyes may suffer from progressive axial myopia. Trauma or multiple ocular surgeries may be predisposing factors.

Cataract Extraction↗

PubMed1987

A locus for a human hereditary cataract is closely linked to the gamma-crystallin gene family.

Within the human gamma-crystallin gene cluster polymorphic Taq I sites are present. These give rise to three sets of allelic fragments from the gamma-crystallin genes. Together these restriction fragment length polymorphisms define eight possible haplotypes, three of which (Q, R, and S) were found in the Dutch and English population. A fourth haplotype (P) was detected within a family in which a hereditary Coppock-like cataract of the embryonic lens nucleus occurs in heterozygotes. Haplotype P was found only in family members who suffered from cataract, and all family members who suffered from cataract had haplotype P. The absolute correlation between the presence of haplotype P and cataract within this family shows that the gamma-crystallin gene cluster and the locus for the Coppock-like cataract are closely linked [logarithm of odds (lod) score of 7.58 at its maximum at phi = 0]. This linkage provides genetic evidence that the primary cause of a cataract in humans could possibly be a lesion in a crystallin gene.

Cataract↗

PubMed1993

Photochemically induced cataracts in rat lenses can be prevented by AL-3823A, a glutathione peroxidase mimic.

Oxidative stress is known to cause cataracts in lens culture systems and is believed to be an important factor contributing to human cataracts. In this communication, it is demonstrated that cataract development of cultured rat lenses produced as a result of photochemically induced oxidation in a 4% oxygen atmosphere similar to the native environment of the lens can be blocked by the transition metal complex AL-3823A. In this system, riboflavin is added to the medium as a photosensitizer. AL-3823A acts primarily as a glutathione peroxidase mimic, which catalytically metabolizes H2O2 and also has low superoxide dismutase-like activity. Measurements of H2O2, O2.-, and OH. indicate that appreciable levels of the first two of these oxidants and low levels of OH. are produced by this photochemical stressing system. The H2O2 concentrations are similar to those found in some patients with cataracts. The development of cataracts was followed over a 96-hr period. Transparency, hydration, glyceraldehyde-3-phosphate dehydrogenase activity, and protein and nonprotein thiol were monitored. All parameters show marked changes during the 96-hr period. However, in the presence of 200 microM AL-3823A, no difference between control and light-exposed lenses was observed with respect to these parameters. The results suggest that in vivo human cataract development caused by oxidative stress may be prevented by compounds of this type.

Animals↗

PubMed1997

On the nature of hereditary cataract in strain 13/N guinea pigs.

PURPOSE: Congenital nuclear cataracts in strain 13/N guinea pigs are caused by a single splice-site mutation in the zeta-crystallin gene. Very little is known of the physical factors involved in lens opacification of this system. The aim of this study is to elucidate the biophysical processes causing the nuclear turbidity. METHODS: Normal, homozygous and heterozygous mutant guinea pig lenses were studied. Polarized light scattering measurements were performed on thin sections of lenses as a function of scattering angle. Scattering intensities were collected in two modes, I- and I+. The total water content of lenses was determined by thermogravimetric analysis. The nonfreezable (bound) water content was obtained by differential scanning calorimetry. The morphology of lenses was investigated by scanning electron microscopy. RESULTS: Normal lenses scatter 5- to 10-fold less light than cataractous lenses at wide angles in both modes. The intensity ratios of the two modes imply that most of the scattering comes from density fluctuations; 10-20% of the turbidity may be contributed by orientation fluctuations. The nucleus of heterozygous cataractous lenses contain less total water than normal lenses, whereas the cortex has the same hydration as the normal lens. The nonfreezable water content of the cataractous nucleus is higher than that of the normal lens. Scanning electron microscopy showed frequent truncation of the fiber cells, cavitations and occasional longitudinal splitting resulting in hollow cylinder formation in the nucleus of the cataractous lens. CONCLUSION: Mutation of zeta-crystallin in guinea pigs causes a congenital cataract. A number of supramolecular events contribute to the turbidity. The mobile water leaves the nuclear fiber cells, causing a collapse of supramolecular structures. Both the size of the aggregates and their refractive index increase by this dehydration process, contributing to the turbidity. The truncation and hollowing of fiber cells causes the orientation fluctuations that also increase turbidity.

Animals↗